Electronic control unit and method for storing rewrite count of nonvolatile memory

1. An electronic control unit comprising: an electrically erasable and rewritable read-only nonvolatile memory storing a control program and control data for a predetermined control object to be controlled, so that the control object is regulated in normal operation according to the control program and the control data stored in the nonvolatile memory, and rewriting processing is carried out to replace contents stored in the nonvolatile memory with contents received from an external device when a predetermined rewrite condition is met; and count storing processing means through which count information for indicating a rewrite count of the contents stored in the nonvolatile memory is stored into a count information storage region allocated in the nonvolatile memory each time the rewriting processing is carried out, wherein the count information storage region is set up as a memory area covering a plurality of addresses in the nonvolatile memory, and in each execution of the rewriting processing, the count storing processing means selects a data-unwritten address in the count information storage region, and then writes numeric value data representing a rewrite count of the contents stored in the nonvolatile memory to the selected address as the count information.

2. An electronic control unit as claimed in claim 1, wherein the count information storage region is set up as a memory area covering a plurality of consecutive addresses in the nonvolatile memory, and in each execution of the rewriting processing, the count storing processing means selects a data-unwritten address in the count information storage region in ascending order of addresses starting from the top address of the count information storage region, and then writes numeric value data representing a rewrite count of the contents stored in the nonvolatile memory to the selected address.

3. An electronic control unit comprising: an electrically erasable and rewritable read-only nonvolatile memory storing a control program and control data for a predetermined control object to be controlled, so that the control object is regulated in normal operation according to the control program and control data stored in the nonvolatile memory, and rewriting processing is carried out to replace contents stored in the nonvolatile memory with new contents received from an external device when a predetermined rewrite condition is met; and count storing processing means through which count information for indicating a rewrite count of the contents stored in the nonvolatile memory is stored into a count information storage region allocated in the nonvolatile memory each time the rewriting processing is carried out, wherein the count information storage region is set up as a memory area covering a plurality of consecutive addresses in the nonvolatile memory, and in each execution of the rewriting processing, the count storing processing means selects a data-unwritten address in the count information storage region in ascending order of addresses starting from the top address of the count information storage region, and then writes numeric value data representing a predetermined constant value to the thus selected address as the count information.

4. An electronic control unit as claimed in claim 3, wherein the predetermined constant value is 0.

5. A method for storing count information indicating a rewrite count of contents stored in an electrically erasable and rewritable read-only nonvolatile memory into a count information storage region allocated in the nonvolatile memory so that an electronic control unit regulates a predetermined control object to be controlled in normal operation according to a control program and control data stored in the nonvolatile memory, and the electronic control unit carries out rewriting processing to replace the contents stored in the nonvolatile memory with new contents received from an external device when a predetermined rewrite condition is met, the nonvolatile memory rewrite count storing method comprising the steps of: setting up a count information storage region as a memory area covering a plurality of addresses in the nonvolatile memory; and in each execution of the rewriting processing, selecting a data-unwritten address in the count information storage region, and then writing numeric data representing a rewrite count of the contents stored in the nonvolatile memory to the selected address as the count information.

6. A nonvolatile memory rewrite count storing method as claimed in claim 5, wherein the count information storage region is set up as a memory area covering a plurality of consecutive addresses in the nonvolatile memory, and in each execution of the rewriting processing, a data-unwritten address in the count information storage region is selected in ascending order of addresses starting from the top address of the count information storage region, and then numeric data representing a rewrite count of the contents stored in the nonvolatile memory is written to the thus selected address.

7. A method for storing count information indicating a rewrite count of contents stored in an electrically erasable and rewritable read-only nonvolatile memory into a count information storage region allocated in the nonvolatile memory so that an electronic control unit regulates a predetermined control object to be controlled in normal operation according to a control program and control data stored in the nonvolatile memory, and the electronic control unit carries out rewriting processing to replace the contents stored in the nonvolatile memory with new contents received from an external device when a predetermined rewrite condition is met, the nonvolatile memory rewrite count storing method comprising the steps of: setting up a count information storage region as a memory area covering a plurality of consecutive addresses in the nonvolatile memory; and in each execution of the rewriting processing, selecting a data-unwritten address in the count information storage region in ascending order of addresses starting from the top address of the count information storage region, and then writing numeric value data representing a predetermined constant value to the selected address as the count information.

8. A nonvolatile memory rewrite count storing method as claimed in claim 7, wherein the predetermined constant value is 0.